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Thursday, May 26, 2016

Insulin is often presented as a hormone that is at the core of the diseases of civilization, particularly because of the insulin response elicited by foods rich in refined carbohydrates and sugars. What is often not mentioned is that protein also elicits an insulin response and so do foods where carbohydrates are mixed with fat. Sometimes the insulin responses are way more than one would expect based on the macronutrient compositions of the foods.

Holt et al. (1997; full reference at the end of this post) conducted a classic study of insulin responses. This study has been widely cited, and paints an interesting picture of differences in insulin responses to various foods. But you have to be careful where you look. There has been some confusion about the results because of the way they are often reported in places like Wikipedia and on various Internet sites that refer to the study.

The key thing to bear in mind when reviewing this study is that the amounts of food used were designed to have the same calorie content: 1000 kJ or 240 kcal (i.e., 240 calories). This led to wild variations in the size of the portions that are compared and their weight in grams. Also, some of the food portions are probably not what people usually eat in one sitting.

In Holt et al.’s (1997) study the participants were 41 lean and healthy university students. They were fed 1000 kJ (240 kcal) portions of the test foods on separate mornings after a 10-hour fast overnight. Blood insulin levels were measured at different times within a 120-minute period after each meal. An insulin score was then calculated from the area under the insulin response curve for each food; white bread was used as the reference food.

Part of Table 2 on page 1267 is shown below (the full text version of the paper is linked at the end of this post), just to illustrate the types and amounts of food served, and the macronutrient breakdown for each food. I hope you can see what I meant when I said that some of the food portions are probably not what people usually eat in one sitting. I don’t think it would be hard to find someone who would eat 158 g of beef steak in one sitting, but 333 g of fish is a little more difficult. Fish has a higher proportion of protein than beef steak, and thus is more satiating. The same goes for 625 g of orange, about 6 oranges. Foods that have more fat have more calories per gram; hence the smaller portions served for high-fat foods.

Table 4 of the article is a bit long, so I am providing it in two parts below. AUC stands for “area under the curve”. As you can see, for isocaloric portions of different foods (i.e., with the same amount of calories), there is a huge variation in insulin response. The insulin AUCs are shown on the second numeric column from the left. Also note that the insulin responses (AUC) for white bread varied in different meals. This complicates things a bit, but at least provides a more realistic view of the responses since each participant served as his or her own control.

Look at the third column from the right, which shows the insulin responses per gram of each food, compared with the response to white bread, always shown at the top for each group of related foods (e.g., protein-rich foods). The gram-adjusted response for whole-meal bread is rather high, and so is the glucose response. The gram-adjusted insulin response to potatoes is less than one-third of the response to white bread, even though the non-gram-adjusted glucose response is higher. The insulin response to beef is also less than one-third of the response to white bread, gram-for-gram. Even cheese leads to a gram-adjusted response that is about half the one for white bread, and I don’t think many people will eat the same amount of cheese in one sitting as they would do with white bread.

In summary, insulin responses to protein-rich foods are often 50 to 70 percent lower than responses to equivalent amounts of refined carbohydrate-rich foods. Also, insulin responses to unrefined carbohydrate-rich foods (e.g., potato, fruits) are often 70 to 90 percent lower than responses to equivalent amounts of refined carbohydrate-rich foods.

Why do insulin levels go up in response to dietary protein?

One of the reasons is that insulin is needed for tissue protein synthesis. That is, increased circulating protein (as amino acids) and insulin have a net anabolic effect, promoting muscle growth and inhibiting muscle breakdown. (Muscle protein synthesis and breakdown happen all the time; the net effect defines whether muscle grows or shrinks.) In this respect, insulin acts in conjunction with other hormones, such as growth hormone and insulin-like growth factor 1.

21 comments:

I'd be interested to see this same experiment carried out on keto-adapted individuals. I would imagine that the generalisation of proteins eliciting a lower insulin response than the equivalent calorific amount of carbs to hold. But with greater insulin sensitivity I wonder if this would still be in the 50-70% range?

It should be noted insulin is a very important metabolic hormone which does more than store body fat and lower glucose. A major role of insulin is regulating, storing electrolytes amino acids and minerals.

Also, protein does result in a lot of glucagon and glucose being made, both of which will stimulate insulin release so as to keep blood sugar stable.

Protein is not as bad as carbohydrate in terms of hypoglycemia because protein stimulates glucagon as well as insulin which helps prevent hypo attacks... although as a person with hypoglycemia, when I was less controlled (before discovering chromium and inositol), I did often get see saw blood sugar from protein. I would get hunger attacks 1.5 hours after a large protein meal, correlating well with insulin surge. This no longer happens after taking lots of chromium and inositol for several months, fortunately... and I can also tolerate carbohydrate much better after taking chromium and inositol.

But either way, I would have to agree, protein is something people with blood sugar problems need to watch. It isn't as bad as carbohydrate, but it is by no means a free food. The only free foods are those which are high in fat and not particularly insulinogenic.

I eat half my body weight in peanuts and almonds... the reason I do that is because I always knew peanuts and almonds kept me stable. I am not at all surprised to see peanuts are the least insulin stimulating foods there are. There is a reason I feel so balanced and have low hunger when I eat them. Pretty much my food choices mirror this graph. I eat eggs, peanuts a whole lot. Bread and beans like never.

What do you make of this statement?:"Research in which study subjects served as their own controls, for example, has shown that under fasting conditions a quarter pound of beef raises insulin levels in diabetics as much as a quarter pound of straight sugar.[74]" [74] Diabetes care 7(1984):465.

"What they overlook is that "protein- and fat-rich foods may induce substantial insulin secretion" as well.[73]Research in which study subjects served as their own controls, for example, has shown that under fasting conditions a quarter pound of beef raises insulin levels in diabetics as much as a quarter pound of straight sugar.[74]"[73] American Journal of Clinical Nutrition (1997):1264.[74] Diabetes care 7(1984):465.

- From: http://www.imminst.org/forum/index.php?showtopic=42451

---Do you think the spike and plunge of high carbohydrate diets are anywhere on par with protein spikes regarding pathogenesis of insulin resistance?

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC524031/ In diabetics: "dietary protein replaced part of the carbohydrate... This resulted in... a modest increase in insulin concentration"

I try to ameliorate the blood sugar and insulin effects of my carb intake dinner meals with immediate sprinting but how do I do so with *protein* containing meals (meals also contain fat&carbohydrate)?

I don't think so. Protein induces an insulin response, but it induces a number of other responses. For example, protein also induces a glucagon response, which balances the effect of insulin. In normoglycemic folks, the result is a zero glucose response. See the graph on this post:

Sprinting after eating may not be such a good idea; it doesn't seem very natural, and may cause digestive problems.

A better approach may be to check your glucose levels after you eat, and avoid those foods that raise them > 140 mg/dl (a rough rule of thumb). When it comes to avoiding health problems and improving lifespan, postprandial glucose control is key:

Sorry rick, wrong graph. That was for cortisol. I can't find one for glucose. Still, in normoglycemic individuals, the glucose response to protein is very small relative to the glucose response to carbs. On a graph, it looks like a "non-response".

The same is true for fat, but fat doesn't induce an insulin response either. That's pure fat I'm talking about; no protein or carbs, not even trace amounts.

My diet at the moment involves fasting for 12-14 hrs and eating for 6-8 hours (skipping breakfast and lunch) - kind of similar to 'leangains.com blog' and book 'Warrior Diet.' I try to limit carbohydrates as low as tolerable (fats are eaten in natural animal and nut states), but when I feel the need to eat starch or fruit (and "carb reload") I immediately sprint in vibram five fingers on grass to become insulin sensitive (I can feel the hyperglycemia and want to immediately lower it - this book I am reading called The CR Way recommends *walking* for 30 minutes and checking blood sugars after meals and exercise walking after meals - they are generally higher carbohydrate diet and lower fat, meeting the ~60g RDA protein but they also skip dinner and fast). I do not practice this diet, but was intrigued by their post meal exercising. I do not walk because of time involved to do it (and I am mid-20s and can tolerate sprinting) and Mark Sisson posted a lot of benefits to sprinting http://is.gd/cPJrb http://is.gd/cPJsX http://is.gd/cPJub <-you don't have to click these links now just referencing)

I believe cardiologist Dr William Davis is a believer in exercise controlling postprandial blood sugars http://is.gd/dLBm6 [#1] Exercise: the fountain of anti-AGEing?

Regarding it being not natural: I just noticed my puppy (would be fed once a day) and have the most energy and want to high-intensity play (and poop) directly after eating a large meal of higher quality grain-free "Timberwolf" brand dog food. Perhaps because fasting lowers ATP energy metabolism (I do not feel the energy levels or drive to do strenuous work in a 12+hr fasted state, however Sisson and leangains do workout in fasted states). But in a fasted state, I do feel more energized after drinking green/white tea ([#2] does green tea (caffeine?)stimulate fat/glycogen mobilizing hormones and do you have any data on tea and increased cortisol levels? -- I have heard of coffee increasing undesirable cortisol from Dr. Perricone's books and he always recommends tea instead). I feel fine not eating or drinking anything at all and being slightly lethargic (not wanting to do strenuous or high intensity activity). [#3] Do you believe fasting (independent of external stressors like work, news, daytime events) increases cortisol in a negative fashion?

The reason I sprint after a meal is to lower blood sugar by converting it to glycogen (and hopefully reduce glycation), then use the stored glycogen for the fasting state for brain, red blood and kidney cells during sleep and the next day. I understand this to be protein sparing.http://is.gd/dLBmT (~5 min in. UC Berkeley Nutrition lecture on fasting and homeostasis: insulin goes down, glucagon hormone goes up, glucose goes down and reaches equilibrium, liver glycogen is depleted, fatty acids used for energy go up (lipolysis), ketones goes up).

[#4] I wonder if I eat higher protein, instead of carbohydrate, if the insulin response is controllable (I believe insulin response can be controlled through exercise when eating carbohydrate through increased insulin sensitivity), or does exercise improve insulin response (spike) to protein ingestion as well? [#5] Can you become hypoglycemic easily on a higher protein, lower carbohydrate diet if not mild-keto/fasting-adapted? And when you personally eat meals do you advocate eating the protein and fat first to lower glycemic impact of vegetable carbohydrates? Dr Perricone recommends this, especially for fruit.

[#6] This seems unnatural but: what are your thoughts on messing with the glycemic impact of carbohydrate foods (cinnamon and vinegar http://is.gd/dLBoe )

My goal is to reduce total life-accumulated insulin and cortisol as another book I am currently reading, 'Transcend', says the two hormones of "aging" are cortisol and insulin. I recall an excerpt in Good Calories, Bad Calories on Alzheimer's and 'insulin degrading enzyme' competing http://textsnip.com/177fcc ('Transcend' too recommends avoiding high-glycemic foods and sugars to lower both insulin and cortisol, like your post, but is not keen on saturated fat - but do mention the VAP test in a positive fashion) and they also say dehydroepiandrosterone [DHEA], growth hormone, and melatonin are the hormones of youth (pg 74 http://is.gd/boM2f and are desired naturally).

[#7]I am also interested in reducing oxidative stress - does high blood sugar (by eating carbohydrates or increasing gluconeogensis) exacerbate this? And what about ketones? I am currently assuming (without statistical data) there is a balance of all 3 needed and that is why my regimen looks like this (majority time is fasting/catabolic state: glycogen depletion, gluconeogensis, ketone for energy).

#1,2,3,4,5,6,7 Number labeling is due to my post being disjointed and I wanted to bring attention to the questions to receive proper responses (no need to answer all right now or anything, a small trickle of good information [as well as links to your previous blog posts] appreciated). And if you can clear up inconsistencies or better approaches in your opinion, please do, as I just started this fasting program - thank you.

Hi rick, here are some general thoughts based on the issues you raised.

Sprinting after exercise is likely to move blood away from where it is needed, the digestive tract, and into muscle tissue. Digestion may be compromised, and muscle uptake of glucose will probably increase a bit. These two things combined will reduce blood glucose levels after the meal. Is this a good thing? It doesn't sound very good to me.

Inducing vomiting after a meal may also reduce the glucose response to the meal, but doesn't sound like a good idea to me either.

Walking is another story. It will have the opposite effect. When you walk you legs act like a "second heart", helping pump blood where it is needed. That will be the digestive tract. Muscle uptake of glucose will increase a little bit, not much, because walking is most a fat-fueled activity.

I generally think that if you avoid the bad things (e.g., refined carbs and sugars, vegetable oils, stress), and do the good things (eat mostly natural whole foods, exercise sensibly, sleep well, have productive social relationships), good health will follow.

Our Stone Age ancestors did not count calories, nor the grams of each macronutriet they consumed. I cannot imagine any Stone Age ancestor thinking something like this: "I need to eat some carbs so that my glycogen stores are replenished for the buffalo hunt ahead". They were smart, probably as smart as we are, but didn't have the knowledge. They had to rely on their hunger regulation systems and their own feelings of well being to guide them.

If you are insulin resistant, or have another condition, that is another story. The first step is to see a doctor, and discuss health issues with her/him thoroughly.

Excellent post, actually I've been looking for this kind of information and some patients with type 2 diabetes may eventually require insulin if other medications fail to control blood glucose levels adequately, though this is somewhat uncommon. 23jj

Insulin causes glucose transporters to bring the glucose into the cell; so does intense exercise. Presumably, the latter would lessen the total insulin response since glucose would be removed from the blood quicker, before it triggered additional insulin release from the pancreas.

The situation is a bit more complex, as protein intake also induces the secretion of glucagon by the pancreas. Without glucagon, the insulin secreted in response to protein intake could lead to dangerously low blood glucose levels.

Ned Kock

About Me

I strongly believe that lifestyle, nutrition and exercise habits that are compatible with our evolutionary past are the key to optimal health. On the other hand, I do not believe that closely mimicking life in the Paleolithic is optimal for health, or even viable. I am a researcher, software developer, consultant, and college professor. Two of my main areas of research are nonlinear variance-based structural equation modeling, and evolutionary biology as it applies to the study of human-technology interaction. My degrees are in engineering (B.E.E.), computer science (M.S.), and business (Ph.D.). I am interested in the application of science, statistics, and technology to the understanding of human health and behavior. I blog about evolution, health, statistics, and technology. My personal web site contains links to my contact information and freely available articles related to the topics of my blogs: nedkock.com.

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